The present invention relates to a method of guiding an unmanned vehicle.
In order to properly guiding an unmanned vehicle, there is a necessity for knowing the position where the vehicle is located on a moving passage. Japanese Patent Application No. 93406/1982 discloses a technical concept that a plurality of ground marks are placed at proper positions on the moving passage and the correct position of the vehicle can be measured by detecting them from the vehicle.
However, this conventional method has a problem that means for detecting the ground marks requires a wide visual scope, and producing such detecting means is expensive.
On the other hand, a so-called navigational guiding method for guiding a vehicle along a previously taught moving passage has been hitherto employed in aircraft or ship. When this navigational guiding method is carried out, direction detecting means and movement distance detecting means are used to estimate the current position of an unmanned vehicle, but error in estimated value of position is increasingly accumulated due to slippage of the vehicle, ruggedness of ground or the like factor. Accordingly, the current correct position of the vehicle is obtained and the estimated value is then corrected with reference to the current correct position.
In this case, it is naturally necessary to teach the position of the ground marks previously.
To teach positions of each ground marks and certain points on the passage, these positions must be measured previously. However, such measurement requires long time and many man hours. Particularly, in the case where there is a necessity for frequently changing the moving passage, it is very troublesome to carry out such measurement.
In the navigational guiding process, the position of each ground point on the moving passage is successively given as target position for the vehicle, but there arises a problem that malfunction such as delayed steering or the like takes place due to improper timing of giving target points.
Further, in the conventional navigational guiding process, controlling is effected for orienting the fore wheels as seen in the direction of movement toward the target point. However, in the case where a fore wheel stearing vehicle is operated or in the case where a rear wheel stearing vehicle is driven in the backward direction, the navigational guiding process fails to function properly.